* [PATCH] perf/x86/amd/power: Use div64_u64 onstead of do_div()
@ 2024-04-28 16:40 Jules Irenge
2024-05-02 16:25 ` David Laight
0 siblings, 1 reply; 2+ messages in thread
From: Jules Irenge @ 2024-04-28 16:40 UTC (permalink / raw)
To: mark.rutland
Cc: alexander.shishkin, jolsa, irogers, adrian.hunter, bp,
dave.hansen, x86, hpa, linux-perf-users, linux-kernel
do_div() truncates a u64 divisor to 32 bit.
This can lead to non-zero being truncated to zero for division.
Fix coccinelle warning
WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead
Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
---
arch/x86/events/amd/power.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/events/amd/power.c b/arch/x86/events/amd/power.c
index 37d5b380516e..ff003c1a645b 100644
--- a/arch/x86/events/amd/power.c
+++ b/arch/x86/events/amd/power.c
@@ -64,7 +64,7 @@ static void event_update(struct perf_event *event)
delta *= cpu_pwr_sample_ratio * 1000;
tdelta = new_ptsc - prev_ptsc;
- do_div(delta, tdelta);
+ div64_u64(delta, tdelta);
local64_add(delta, &event->count);
}
--
2.43.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* RE: [PATCH] perf/x86/amd/power: Use div64_u64 onstead of do_div()
2024-04-28 16:40 [PATCH] perf/x86/amd/power: Use div64_u64 onstead of do_div() Jules Irenge
@ 2024-05-02 16:25 ` David Laight
0 siblings, 0 replies; 2+ messages in thread
From: David Laight @ 2024-05-02 16:25 UTC (permalink / raw)
To: 'Jules Irenge', mark.rutland
Cc: alexander.shishkin, jolsa, irogers, adrian.hunter, bp,
dave.hansen, x86, hpa, linux-perf-users, linux-kernel
From: Jules Irenge <jbi.octave@gmail.com>
> Sent: 28 April 2024 17:40
>
> do_div() truncates a u64 divisor to 32 bit.
> This can lead to non-zero being truncated to zero for division.
>
> Fix coccinelle warning
> WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead
>
> Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
> ---
> arch/x86/events/amd/power.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/events/amd/power.c b/arch/x86/events/amd/power.c
> index 37d5b380516e..ff003c1a645b 100644
> --- a/arch/x86/events/amd/power.c
> +++ b/arch/x86/events/amd/power.c
> @@ -64,7 +64,7 @@ static void event_update(struct perf_event *event)
> delta *= cpu_pwr_sample_ratio * 1000;
> tdelta = new_ptsc - prev_ptsc;
>
> - do_div(delta, tdelta);
> + div64_u64(delta, tdelta);
Nak - you've not tested it.
David
> local64_add(delta, &event->count);
> }
>
> --
> 2.43.2
>
-
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2024-04-28 16:40 [PATCH] perf/x86/amd/power: Use div64_u64 onstead of do_div() Jules Irenge
2024-05-02 16:25 ` David Laight
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